Sensor Installation Guidelines - Watlow 945 Series User Manual

How to Wire the Series 945
The Series 945 wiring is illustrated by model number option. Check the terminal
designation sticker on the control and compare your model number to those shown
here and also the model number breakdown on the inside back cover of this manual.
Series 945 internal circuits appear "inside" the line drawing of the 945, while
connections and terminal designations appear "outside" the line drawing. All
outputs are referenced to a de-energized state. The final wiring figure is a typical
system example.
When you apply power without a sensorinput on the terminal strip, the 945
displays "- - - -" in the upper display, and "0" in the lower display. Press AUTO/
MAN twice, and ER 7 is displayed for one second. This error indicates an open
sensor or A/D error. Remove power to the control and connect the sensor properly,
see Page 6. All wiring and fusing must conform to the National Electric Code and
to any locally applicable codes as well.

Sensor Installation Guidelines

We suggest you mount the sensor at a location in your process or system where it
reads an average temperature. Choose a point that will adequately represent the
process temperature without being overly reactive.
For thermocouple inputs: Use an isolated or ungrounded thermocouple if an
external 4-20mA output device with a non-isolated circuit common is connected.
Extension wire must be of the same alloy as the thermocouple itself to limit errors.
For RTD inputs: There could be a +2°F input error for every 1 of lead length
resistance when using a 2 wire RTD. That resistance, when added to the RTD
element resistance, will result in erroneous input to the instrument. To overcome
this problem, use a 3 wire RTD sensor, which compensates for lead length resis-
tance. When extension wire is used for a 3-wire RTD, all wires must have the
same electrical resistance (i.e. same gauge, copper stranded).
For 0-5VDC or 4-20mA process inputs: The rL and rH settings scale the display
to match the measured range of the process signal. For 0-5VDC process input, the
impedance is 100KΩ. For 4-20mA process input, the impedance is 249Ω.
Install and Wire, Chapter 2
Fuse
11
12
13
120 VAC
10
Fuses
12
13
240 VAC
L1
L2
Earth Ground
L1
L2
Earth Ground
WATLOW Series 945 User's Manual
Power Wiring
Figure 5 -
120 VAC Power
Wiring
Figure 6 -
240 VAC Power
Wiring
WARNING:
To avoid potential
electric shock, use
National Electric
Code (NEC) safety
practices when
wiring and connect-
ing this unit to a
power source and to
electrical sensors or
peripheral devices.
5